Battery swelling, leaking or smelling

Safety box: if the battery is swollen, hot, hissing, smoking or leaking

1. Do not touch, press or try to move the battery.
2. If it is safe to reach them, switch off in the manufacturer's sequence: usually the inverter output and power, then the battery breaker, then the battery's own power switch. Your installer should have shown you these at handover.
3. Keep children and others out of the room. Open a window or door to ventilate if you can do so without going near the battery.
4. Move flammable items away only if they are well clear of the battery.
5. If there is smoke, fire, a strong chemical smell or popping sounds, get everyone out and call Rescue 1122. Tell them there is a lithium battery. Do not use water on live electrical equipment.

What lithium battery swelling means

A lithium battery is built from many cells. Inside each cell, the electrolyte can break down when the cell is pushed outside its safe limits. That breakdown releases gas. Pouch cells puff up like a pillow; hard-cased prismatic cells push out at their sides. In a home solar battery, the cells sit inside a metal case, so the case itself may bulge, a side panel may bow, the battery may no longer sit flat in its rack, or a cabinet door may not close properly.

Gas inside a cell means it has been damaged. A swollen cell can heat up, vent or, in the worst case, enter thermal runaway, where it overheats, releases flammable gas and heats the cells next to it. Our solar fire safety guide explains thermal runaway in more detail.

Is a swollen battery dangerous?

Yes. Treat any swollen battery as damaged and unsafe to use. It may not fail soon, but you cannot know how close it is, and every charge and discharge adds stress to a damaged cell.

LiFePO4 swelling

Most home and commercial solar batteries use lithium iron phosphate (LiFePO4). It is generally regarded as more thermally stable than some other lithium chemistries, which lowers the fire risk. It does not make swelling harmless. LiFePO4 cells can still swell from overcharge, over-discharge, heat or a defect, and a swollen LiFePO4 battery should be handled the same way. Some prismatic LiFePO4 cells expand very slightly during normal charging and are held in place by the module's fixtures; a visible bulge in the battery case is not normal. For a comparison of chemistries, see LiFePO4 vs tubular battery.

Quick-check table

Why lithium batteries swell

1. Overcharging. Charge voltage set too high for the battery, or a battery type set wrongly in the inverter, pushes cells past their limit. This is more likely when the battery and inverter are not communicating, so the inverter charges on typed-in settings instead of the battery's own limits. See battery and inverter communication.
2. Deep discharge. A battery left flat for weeks, for example after a long fault or storage at 0%, can damage its cells. Charging a deeply discharged battery without the manufacturer's procedure adds stress. See lithium battery not turning on.
3. Heat. A battery in direct sun, in a closed cupboard or next to the inverter's hot exhaust ages faster and is more likely to swell. Placement rules are in where to install your inverter and battery.
4. Cell imbalance and a weak BMS. If one cell drifts far from the others and the BMS does not protect it, that cell can be overcharged even when the pack voltage looks normal. See battery management system explained.
5. Physical damage. A battery dropped in transport, knocked, crushed or flooded can be damaged internally.
6. Age and poor-quality cells. Ageing cells produce more gas, and low-grade or recycled cells are more likely to swell early.
7. Mixing batteries. Adding a new battery alongside an old one of a different make or age can push the weaker one harder. See replacing or expanding your solar battery.

Safe owner checks

Only do these from a safe distance and if there is no smoke, fire or strong smell.

1. Look, do not touch. Check from a step or two away whether the case looks bowed, the battery has shifted, or the door is pushed out.
2. Read the app or inverter screen. Note battery temperature, state of charge, charge current and any BMS alarm such as over-voltage, over-temperature or cell fault.
3. Switch off in the manufacturer's sequence if it is safe to reach the switches.
4. Take photos of the battery, its label and serial number if visible without touching it, and the screen or app alarms.
5. Ventilate and keep people away.
6. WhatsApp your installer with the photos, battery and inverter model, and when you first noticed it.

Do not open the battery case, loosen terminals, press the bulge, move the battery to "let it cool", put it in water or try to charge it to see if it still works. Opening the case can also void the manufacturer's warranty.

What an engineer will check

• The battery itself. Whether it is safe to stay where it is for now, or needs moving to a safe, ventilated area by trained staff with suitable protection.
• BMS logs. Cell voltages, temperatures and event history, to see whether the battery was overcharged, over-discharged or overheated.
• Inverter settings. Battery type, charge voltage, charge current and cut-off settings against the battery maker's limits.
• Communication. Whether the battery and inverter were communicating properly, and whether the pair is on each maker's compatibility list.
• Location and heat. Sun, ventilation, nearby heat sources and clearances.
• Other batteries in the bank. In a multi-battery system, each one is checked; if one swelled, the cause may affect the others.
• Warranty claim. Collecting the evidence the manufacturer needs. Manufacturer warranty applies per product under its own written terms.
• Safe disposal. A swollen battery should not go in household waste or to a scrap dealer who will open it. See disposing of old solar panels and batteries.

How to prevent swelling

• Use a battery that is approved for your inverter, with closed-loop communication working.
• Keep the charge settings the installer and battery maker set; do not raise voltage or current to "charge faster".
• Install the battery in a shaded, ventilated, dry place away from heat and sun.
• Avoid leaving the battery fully empty for long periods; follow the manufacturer's storage instructions if the system will be off.
• Do not mix old and new or different-brand batteries without the engineer's approval.
• Watch for early warnings: rising temperature, BMS alarms, a battery that beeps (see lithium battery beeping) or backup time dropping sharply.

Our lithium battery care guide covers everyday habits that also extend battery life.

How Solar Works Pakistan handles battery complaints

We supply lithium batteries and BESS from Luminey and current Huawei and Sungrow options, matched to compatible inverters, and we check battery-inverter communication at commissioning. Manufacturer warranty applies per product. For systems we install, our own engineering staff handle complaints, our 1-year service warranty applies under the applicable project terms, and we target sending service personnel within 48 hours of a registered complaint to begin diagnosis. See how after-sales service works. For replacement options, see our lithium battery price guide.

Frequently asked questions

Why is my lithium battery swelling?

Swelling comes from gas inside the cells, usually caused by overcharging, deep discharge, heat, physical damage, age or a defect. Wrong inverter settings or missing battery communication are common causes in solar systems.

Is a swollen battery dangerous?

Yes. A swollen battery is damaged and can overheat, vent or catch fire. Stop using it, switch off safely, keep people away and call an engineer.

Battery bulging: can I still use it?

No. Continued charging and discharging adds stress to damaged cells. Switch it off following the manufacturer's sequence and have it assessed.

Does LiFePO4 swelling happen?

Yes. LiFePO4 is more thermally stable than some lithium types, but its cells can still swell from overcharge, over-discharge, heat or defects. Treat a swollen LiFePO4 battery as damaged.

Can a swollen lithium battery be repaired?

Owners should never open or try to repair one. A qualified technician or the manufacturer decides whether a module or the whole battery must be replaced; damaged cells are not something to reuse.

Is battery swelling covered by warranty?

It depends on the cause and the manufacturer's written terms. Defects are usually covered; damage from heat, wrong settings or physical damage may not be. Keep your invoice, serial number and photos.

How do I dispose of a swollen battery?

Do not put it in household waste or sell it to a scrap dealer who will open it. Ask your installer or the manufacturer's service channel how to return it for safe recycling.

Sources

1. University of Reading Health and Safety Services, "I have a swollen lithium-ion battery: what should I do?" (causes of swelling; do not puncture; stop using; fire response): https://www.reading.ac.uk/health-safety-services/fire-safety/lithium-battery-information/i-have-a-swollen-lithium-ion-battery-what-should-i-do